import sys
sys.setrecursionlimit(10**7)
from functools import lru_cache

@lru_cache(maxsize=None)
def f(n):
    if n == 1:
        return 0
    S = set()
    S.add(f(n//2)^f((n+1)//2))
    if n >= 3:
        S.add(f(n//3)^f((n+1)//3)^f((n+2)//3))
    
    now = 0
    while True:
        if now not in S:
            return now
        now += 1

N = int(input())
print("A") if f(N) else print("B")